Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the tool is a safe read operation. The description adds useful behavioral context by noting the returned data (start/end timestamps with project and file) and the optional slice_by parameter. However, it does not disclose rate limits, authentication prerequisites, or how errors/missing data are handled.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single well-structured sentence that front-loads the purpose and key parameters. It is concise with no redundant words, though splitting into two sentences could slightly improve readability.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given 8 parameters and 0% schema description coverage, the description covers only date and slice_by, leaving other optional filters and the required user_id unexplained. The existence of an output schema covers return values, but the parameter semantics gap makes the description incomplete for an agent to use the tool effectively.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate. It explains the required date parameter with format (YYYY-MM-DD) and the slice_by parameter with possible values (entity/language/branch), but it leaves project, branches, timeout, timezone, user_id, and writes_only unexplained. Even the required user_id is not mentioned, leaving a significant semantic gap.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly and specifically states the tool fetches WakaTime coding durations for a single day, including start/end timestamps and project/file data. It distinguishes itself from sibling tools like heartbeats by explicitly focusing on daily durations and optional slicing by entity/language/branch.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies the intended use case: retrieving daily coding durations with a required date. However, it does not explicitly state when to use this tool over alternatives, nor does it mention any exclusions or recommended conditions. The single-day scope and required date provide clear context, but no comparative guidance is given.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.